Method of manufacturing phosphate fertilizer containing nitrogen.



UNITED STATES PATENT OFFICE.

ANTONIUSFOSS, OF CHBISTIANIA, NORWAY, ASSIGNOR TO'NOR SK HY DRO-ELEKTRI SK KVAELSTOEAKTIESELSKAB, F CHRISTIANIA, NORWAY.

METHOD OF MANUFACTURING PHOSPHATE FERTILIZER CONTAINING NITROGEN.

No Drawing.

To all whom it ma concern:

Be it known t at I, ANTONIUS Foss, a subject of the King of Norway, residing at "Christiania, in the Kingdom of Norway,

- solution, is di method of treating such p have invented certain new and useful Imrovements in Methods of Manufacturlng' ing nitrates with'ready prepared phosphate fertilizers.

It has already been proposed to render phosphates soluble b means of dilute nitric acid, to neutralize t e acid solution and to evaporate themixtureof diphosphate and nitrates thus obtainedto such an extent that it will congealon cooling. Another proposal in effect directly evaporatingthe acid iiicult to carry out as the liquor will strongly attack the plant and also losses of nitric acid will 'easil occur. Both these methods involve a cost y after-treatment of the soluble .product immediately obtained in order to convert, it into a solid fertilizer ca able of being satisfactorily spread.

itherto no roce'ss for rendering hates soluble y means of nitric acid is own that is as equallyosrational as the 'phat'es with sulfuric acid used in the manufacture of superphosphates by which the product from the acid treatment is immediately obtained in the dip state. Experiments that have been made 1n this directlon have only'given pasty masses, which have to be transformed into thedry state either by subse%uent heating or by admixture of water-a sor bing substances such as gypsum, pulverized peat and the like in order to be fit for spreading.

'Such admixtures however, enhance the price of the fertilizer and lower itspercentage of the valuable constituents, phosphoric acid and nitrogen.

I have now ascertained certain novel conditions under which the phosphate material can be rendered soluble by means of Specification of Letters Patent.

hos-

Patented Jan. 21, 1919.

Application filed May 8, 1917. Serial No. 167,338.

nitric acid in such a manner, that a dry product is immediately obtained and only a disintegrating operation is required to make a merchantable article.

The said conditions are firstly, that. use

is made of nitric acid of such a concentration, that no more water is sup lied to the mass, than the latter can absor Then it is of particular importance that the product shall contain suflicient quantities of calcium nitrate as being in this case the water-binding substance and corresponding in this respect to the yp'sum of tie ordinary superphosphate. ccordin to the invention this latter condition is rea lzed by using for the process a raw-material containing calcium carbonate. The calcium carbonate can be added to the phosphatic raw-material before treating it with nitric acid. Experience has, however, proved, that severalsorts of native crude phosphates occur, that have such a content of calcium carbonate that the can be used withoutany admixture.

The strength of the acid used and the percentage of carbonate resent in the crude' material are interde en ent and the quantity and strength of t e acid must be adapted for-the special'raw-material being treated. Very often an acid of about 55-60 per cent. will be found convenient; e

The raw-phosphate containing carbonate is then treated with so much nitric acid of the proper strength that a maxium of soluble components 1s obtained and after completion of the reaction (solution and waterinding) a solid mass results. During the reaction some nitrogen oxids and vapors of nitric acid will-escape and must be recovered. On account of the evolution of carbon dioxid in the mass the latter will be porous and retain some nitrogen oxids. In order to recover these oxids, the mass may be stirred while still semiliquid or asty,

a current of air being simultaneously lown through, or the mass mayfor a-short time be exposed to a vacuum in order to make the nitrogen oxi s escape.

When the mass has solidified, it. can immediately be pulverized and packed. The product contains beside calcium nitrate water-soluble phosphoric acid and a very small amount of insoluble phosphates.

The advantages of the process above described are obvious. Phosphates are rendered soluble by means of nitric acid in such a manner that a-fertilizer is obtained containing nitrogen," which consists in addwhich may be used without any further ing suflicient nitric acid to raw-phosphates treatment just 'as the common superphosassociated with carbonate of calcium to renphate obtained in treating phosphates with der them soluble, stirring the mass while 5 sulfuric acid, but having the merit as com-. in a semi-liquid state, and simultaneously 15 pared with superphosphate that it does not passing a current of air therethrough. contain any dead weight of useless co'nstit- ANTONIUS FOSS. uents. Witnesses I claim; KARL L. LEE, 10 The method of manufacturing fertilizer ,O. VARMAN. 

